Hydrogen has been demonstrated to be a very appealing alternative fuel supply for many applications, including automobiles, because the only by-products of hydrogen consumption are heat and water. Current hydrogen fuel supplies rely upon hydrogen fuel cells to generate electricity from stored hydrogen, which may be used to operate an electric motor to power an automobile. In automotive fuel cell applications, hydrogen is typically stored in a gaseous state in a tank at relatively high pressures approaching 700 bar or 10,000 psi. The high-pressure storage provides a large supply of hydrogen in a reduced storage volume. The fuel cell generally draws hydrogen from the tank through a system of tubes or pipes as needed to maintain energy conversion, but it must be operated at significantly lower pressures (e.g., 200 psi) than the stored hydrogen for reduced system expense and safety. Typically, at least one pressure regulator is provided between the tank and the fuel cell to reduce the pressure of the compressed hydrogen from the tank to a pressure suitable for the fuel cell system.
It is well understood that as the hydrogen is removed from the tank through the pressure regulator, a rapid decrease in pressure of the hydrogen causes a corresponding decrease in the temperature of the hydrogen within the pressure regulator that can approach −50 Celsius. Additionally, in certain environments, the operating temperatures can also reach temperatures of +85 Celsius. Such extreme temperature ranges make sealing the regulator very difficult. For example, at extremely low temperatures, metal-to-metal seals and resilient seals contract causing leaks in the regulator, which may degrade pressure control performance. Conventional design techniques to counteract seal contraction problems involve providing seal-to-sealing surface tolerances and materials of construction that preferably seal at low temperatures. These same design techniques have been known to create “seizing” of regulator components at high operating temperatures as the seals expand and bind to prevent operation of the regulator. Additionally, problems can result from periodic or cyclic dispensing of the hydrogen from the tank.
Depending on the demand for hydrogen from the tank, the pressure regulator can be subjected to repetitive thermal or cooling cycles as the hydrogen is dispensed from the tank. These repetitive cycles can create undesirable operational and maintenance issues with the pressure regulator. For example, many conventional pressure regulators use multi-component interior valve assemblies that rely upon high-pressure seals within the valve assembly. The thermal cycles induce expansion/contraction cycles of the high-pressure seal components that can result in increased seal wear that may produce high-pressure leaks or even catastrophic failure of the regulator and/or the fuel cell system. Therefore, it would be beneficial to provide a pressure regulator that is significantly less susceptible to leaks and operational failures in high-pressure gas dispensing applications.